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Finding the Fourth Proportional to 209.25, 313.88 and 81

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Solution

The fourth proportional to 209.25, 313.88 and 81 is: 121.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.25 : 313.88 = 81 : x
  2. Step 2: Convert to fraction form
    209.25/313.88 = 81/x
  3. Step 3: Cross multiply
    209.25x = 313.88 × 81
  4. Step 4: Simplify right side
    209.25x = 25,423.88
  5. Step 5: Solve for x
    x = 25,423.88/209.25
  6. Step 6: Final answer
    x = 121.50

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.